Table 1.
Characteristics of low (lowest 25%) and high (highest 25%) cognitive reserve (CR) groups according to their age 20 general cognitive ability as measured with Armed Forces Qualification Test (AFQT20).
| Low CR (n=131) | High CR (n=114) | |||
|---|---|---|---|---|
|
| ||||
| M (SD) | M (SD) | F | p | |
| Age | 55.34 (2.60) | 55.82 (2.59) | 0.08 | 0.78 |
| Years of education | 12.91 (1.92) | 14.89 (2.17) | 44.81 | <.001 |
| APOE ε4+/ε4− (% of ε4+)a | 33/95 (26%) | 36/73 (33%) | 1.13 | 0.29 |
| Hippocampus volume (mm3)aa | 8096 (852) | 8282 (759) | 0.01 | 0.99 |
Note. Comparisons based on mixed models, except APOE ε4+ prevalence comparison based on Rao-Scott chi-square test. Twin relatedness controlled in all comparisons.
a
number of individuals with and without APOE ε4 allele and the prevalence of APOE ε4 carriers in parentheses among low (n=128) and high (n=109) CR individuals.
aa
controlled also for estimated total intracranial volume.